The present invention relates to an improvement of moldings made of hydrolyzed ethylene-vinyl acetate copolymer, more particularly to moldings having an improved heat deflection property.
Moldings made of hydrolyzed ethylene-vinyl acetate copolymer are superior to other resin moldings in the properties such as stiffness, hardness, abrasion-resistance and antistatic charge and, therefore, they have been expected to use for so-called engineering plastics such as machine parts, automobile parts, aircraft parts or electric-device parts. However, the copolymer has the disadvantage that the heat deflection temperature thereof is low compared with other known engineering plastics. For instance, the heat deflection temperature of hydrolyzed ethylene-vinyl acetate copolymer having an ethylene content of 30% by mole, a vinyl acetate content of 70 % by mole and a degree of hydrolysis in vinyl acetate component of 99.5 % by mole is only about 70.degree.C. On the other hand, the heat deflection temperature of acrylonitrile-butadiene-styrene resin and acrylonitrile-styrene resin is 86.degree.C. and 83.degree.C., respectively. Therefore, when moldings made of the copolymer are handled at a high temperature or when a temperature of moldings rises during use due to generation of frictional heat, there may cause troubles such as deformation, deflection and distortion, which are great disadvantages for engineering plastics requiring severe dimensional stability.
Hithertofore, incorporation of a filler into a resin has been proposed in order to improve mechanical strength and stiffness of moldings. However, it has never been known and also never been attempted to incorporate talc into hydrolyzed ethylene-vinyl acetate copolymer to raise heat deflection temperature of the copolymer.